Although Oculus Rift's newest updates allow the installation of game and content data on a drive of your choice, your existing data can't easily be moved. I found this article that describes how to do it, but I found that my folder locations were different, and I had to change the order of its instructions in order to succeed. If you're willing to open an elevated command prompt in Windows 10 (a command prompt that has administrator privileges), you can do this pretty easily using the following steps:

Rename the "Software" and "Downloads" folders. I renamed to "Software2" and "Downloads2". This will require you to authenticate to complete.

Copy "Software2" and "Downloads2" to a new folder on your destination drive (I used "D:\Oculus Rift Data"). The destination drive must be formatted NTFS and can't be a networked volume. These folders could be huge, so this might take awhile.

In the new location, rename the folders back to "Software" and "Downloads".